Fig. 2. Dose dependence of agonist-induced cAMP accumulation in cells co-expressing either AC and G₂ or AC-RLuc and GFP-G₂. HEK 293 cells were transfected with vector or with recombinant plasmids so that they expressed the indicated proteins. The cells were treated with different concentrations of isoproterenol before being assayed for cAMP levels. Dose-response curves and EC₅₀ values were generated using GraphPad Prism® software. The EC₅₀ values are reported as the mean ± s.d. for three independent experiments. The data presented in the graph are for a typical experiment in which the maximal agonist-induced increase in cAMP accumulation was 336 pmol cAMP/mg protein/15 minutes for HEK cells that did not express exogenous proteins (Vector) as compared with 5512 and 3070 pmol cAMP/mg protein/15 minutes, respectively for cells expressing either exogenous wild-type or tagged proteins.